Liquids, including water, are commonly used for many domestic and industrial purposes such as drinking, food preparation, manufacturing, processing of chemicals, and cleansing. Often it is necessary to purify a liquid prior to its use. Filters such as ceramic filters are typically used to remove particulate and chemical impurities from liquids. In addition, a liquid can be exposed to UV radiation to neutralize microorganisms and deleterious pathogens that may be present in the liquid. Exposure to short wavelength (e.g., 100 nm-320 nm) UV radiation can have a germicidal effect, i.e., the radiation can disrupt the DNA of many cellular microorganisms—thereby virtually destroying them or rendering them substantially harmless. The exposure to UV radiation can also substantially prohibit the growth and/or reproduction of microorganisms that may be present in the liquid.
The germicidal effect of UV radiation on flowing liquid depends on the energy density of the UV radiation, i.e., the fluence of radiation, which in turn is related to the power of the radiation and the duration of exposure. The radiation power depends on the power supplied to the source of radiation, and the duration of exposure depends on the flow rate of the liquid. However, UV light emitted by LEDs typically has a Gaussian distribution of intensity that may not approximate the exposure volume of the fluid being disinfected. Thus, disinfection systems with such LEDs tend to have non-homogeneous distributions of UV intensity, which results in inefficient disinfection. That is, excess LED power may be required to achieve a desired fluence of radiation within the entire cross-section of the treatment system, even if such elevated power levels produce much more than a required level of fluence within particular areas of the system.
In addition, the power required to disinfect various liquids may require the use of more than one LED in the disinfection system. Although UV LEDs may in theory have lifetimes exceeding 10,000 hours or more, they do fail, and failure of one device in a multiple-LED system tends to result in further uneven distribution of UV irradiance and thus inefficient and/or insufficient disinfection.
In view of the foregoing, there is a need for fluid-treatment systems utilizing UV LEDs for disinfection that efficiently produce homogeneous levels of irradiance and that are robust even in the event of LED failure.